A typical apparatus for making hollow bodies from thermoplastic film has a step-type film feeder, an upper tool arranged above the film and a lower traverse for accommodating a lower tool, in particular a combined shaping and punching tool. The lower traverse is shiftable in a pivotal frame below the film in a vertically slidable manner and can be swung out with the pivotal frame, wherein the lower traverse is connected to a drive via a slider crank drive having cam-controlled crank arms.
An apparatus of this type is known from EP 1 314 536. A lower table or lower traverse slidable on a bridge frame that is pivotal around an axis is held on the pivoting bridge via toggle-linkage arms. The toggle arms are acted on via a first connecting rod by a drive arranged to the side that via a further second connecting rod also causes the pivot motion of the pivoting bridge with the lower traverse. The movements introduced via the two reciprocating rods are controlled by cam disks acting on levers pivoted on the reciprocating rods. The horizontal motion and the pivot motion proceed in an overlapping manner until a certain angular position of the toggle lever arms.
A thermoshaping machine is known from DE 197 10 475 in which the lower traverse or lower table is supported via a pair of levers hinged in a lower bearing block. The lower lever bears via a roller provided under the bearing block articulation point against a driven cam disk rotating at a constant speed. A separate pivoting table carrying the tool is mounted in or on the lower traverse. This pivoting table is connected to the lower traverse by means of a pivot bolt that forms the pivot axis of the table. The pivoting table engages with at least one roller in at least one groove of a cam, whereby, with the lowering movement of the lower traverse controlled by the cam disk via the pair of levers, the separate pivoting table is shifted into a pivoted position to release or receive the finished articles. While the lower traverse moves downward in a straight manner, the roller of the pivoting table follows the curve of the guide groove, so the pivoting table at first performs a straight lowering movement and subsequently a pivot movement in the curved section of the guide groove. The pair of levers that is not rotatable along with the pivoting table is connected to the roller only indirectly via the lower table or lower traverse.
The cam disks have proven to be a disadvantage with the known apparatuses, since a change in the sequence of motions necessitates a complex switching of the cam disks, which furthermore are expensive. Moreover, they are susceptible to faults because of the numerous lever pivot points and necessitate a large construction height, in particular with a lever support of the lower traverse from below, wherein then furthermore the levers and their spherical plain bearings have to absorb the large forces upon closing the tables for shaping and subsequent punching out of the finished articles.